We know that we are of God, and that the whole world is under the power of the evil one.
19 We are of God He deduces an exhortation from his previous doctrine; for what he had declared in common as to the children of God, he now applies to those he was writing to; and this he did, to stimulate them to beware of sin, and to encourage them to repel the onsets of Satan.
Here we have, I. A recapitulation of the privileges and advantages of sound Christian believers. 1. They are secured against sin, against the fulness of its dominion or the fulness of its guilt: We know that whosoever is born of God (and the believer in Christ is born of God, Jo1 5:1) sinneth not (Jo1 5:18), sinneth not with that fulness of heart and spirit...
Commenting on 1 John 5:18-21
And we know that we are of God,.... The sons of God, and regenerated by him; this is known by the Spirit of God, which witnesses to the spirits of the saints that they are the children of God; and by the fruits and effects of regenerating grace, as love to the brethren, and the like: and the whole world lies in wickedness; that is...